Xiang, if multi-phase initialisation is an area you're interested in, it occurs to me you may also want to take a look at Petr's proposal to provide efficient access to global module state from methods of extension types: https://mail.python.org/pipermail/import-sig/2016-August/001065.html

With the 3.6 feature freeze deadline imminent it's looking like that will be deferred to 3.7, but it's still a significant improvement that should encourage greater use of the newer more submodule and reloading friendly approach to C extension module initialisation.